1. Field of the Invention
The present invention relates to an inkjet recording apparatus wherein recording is carried out by discharging ink from a recording head, particularly to an ink supply mechanism between two ink tanks, which are connectable to and removable from each other via joint portions.
2. Related Background Art
Conventionally, there have been the following 3 types of system for supplying ink to a recording head of an inkjet recording apparatus.
(a) Head Cartridge System
As shown in FIG. 8, in the head cartridge system, a head cartridge 103, integrated with a recording head 101 for discharging ink and an ink tank 102 for storing ink to be supplied to the recording head 101, is mounted detachably on a carriage 104 which is supported slidably by a guide shaft 105. The carriage is reciprocated along the guide shaft 105 by a carriage drive mechanism, which is not shown in the FIG. 8. A platen 106 is disposed at a position opposite to the recording head 101, and a record sheet 107 such as paper and film is transferred on the platen 106 perpendicular to the moving direction of the carriage 104 by a record sheet transfer mechanism, which is not shown in the FIG. 8.
And then, while repeating intermittent supply (supplementary scanning) of the record sheet 107 and reciprocating motion (main scanning) of the carriage 104, desired letters and images are recorded on the record sheet 107 by driving the recording head 101 and discharging ink from the recording head 101, on the basis of recording signals. In this system, the ink in the ink tank 102 is supplied directly into the recording head 101.
(b) Tank Cartridge System
As shown in FIG. 9, in the tank cartridge system, only a recording head 111 is mounted on a carriage 114. A tank cartridge 112 for storing ink is disposed on a main body side of an ink jet recording apparatus. The recording head 111 and the tank cartridge 112 are connected each other with a flexible ink supply tube 113 which can follow the movement of the carriage 114 along a guide shaft 115, and the ink in the tank cartridge 112 is supplied into the recording head 111 via the ink supply tube 113.
(c) Pit-In System
As shown in FIG. 10, in the pit-in system, a recording head 121 and a sub-tank 122 are mounted on a cartridge 124. The recording head 121 and the sub-tank 122 are integrated in a one body, and the ink in the sub-tank is supplied directly into the recording head 121. On the other hand, a main tank 123, whose capacity of ink is larger than that of the sub-tank 122, is disposed on a main body side of an inkjet recording apparatus. On the main tank 123 provided is a joint portion 123a, which is communicated with an ink inlet portion 122a provided on the sub-tank 122 when the sub-tank is moved to the facing position against the main tank 123.
When the volume of the ink in the sub-tank 122 decreases less than the predetermined amount as a result of consumption of the ink in the sub-tank 122 by discharging ink from the recording head 121, a carriage 124 is moved along a guide shaft 125 to the position where the ink inlet portion 122a faces the joint portion 123a. At the position, the ink inlet portion 122a and the joint portion 123a are communicated with each other to supply ink from the main tank 123 into the sub-tank 122.
However, there have been problems shown below in the conventional system of supplying ink described above.
In the head cartridge system, it is essential to make a capacity of the ink tank larger in order to reduce exchange frequency of the head cartridge, namely, in order to increase the number of sheets, which can be recorded by a single head cartridge. Since the head cartridge is mounted on the carriage, however, the increase in capacity of the ink tank results in the increase in space necessary for scanning the carriage to thereby require the enlargement of a recording apparatus, and also results in uneasiness of high-speed carriage scanning due to larger weight applied to the carriage.
On the other hand, in the tank cartridge system, the above-mentioned problem is eliminated because the recording head is only mounted on the carriage. Since the recoding head is connected to the tank cartridge with the ink supply tube, however, a complicated mechanism becomes necessary resulting in uneasiness of miniaturization of a recording apparatus.
Besides, in the pit-in system, since ink is supplied from the main tank into the sub-tank and the volume of the sub-tank can be small, size and weight of the structure on the carriage become smaller than those in the head cartridge system, resulting in a simple configuration of the apparatus due to no more need of an ink supply tube.
However, in the pit-in system, since coupling portions between the main tank and the sub-tank (the ink inlet portion 122a and the joint portion 123a in the example shown in FIG. 10) are apart from each other during recording operation, foreign material such as paper powder and dust sticks and piles up onto the coupling portions during their usage for a long time. When the ink is supplied into the sub-tank from the main tank during their coupling, the piled-up foreign material is introduced into the coupling portions and may reach the recording head via the sub-tank. Once the foreign material reaches the recording head, discharge of the ink becomes unstable resulting in no discharge of the ink in the worst case.
Besides, sealing ability of the joint portion may decrease to introduce air into the coupling portions by piling up of the foreign material at the joint portion. Further, since the coupling portions are opened except when supplying ink, the ink filled in the coupling portions becomes dry to adhere as a solid to the interior of the coupling portions. Thus, as a result of introduction of air and adhesion of solid ink, flow resistance of ink in the coupling potions increases, and reliability of supplying ink decreases after all.
The object of the present invention is to provide an ink supply mechanism and an inkjet recording apparatus, wherein ink is supplied in high reliability still employing the pit-in system, which is able to supply ink by only a small and simple configuration.
Another object of the present invention is to provide an ink supply mechanism comprising a first ink tank for storing ink a joint portion connected to said first ink tank and a second ink tank disposed to be movable to said first ink tank and provided with a connection portion connected to said joint portion in order to make ink supply from said first ink tank possible, wherein said joint portion is movable between a connected position where said connection portion is connected thereto and a disconnected position where said connection portion is not connected thereto, and a cap member for sealing a region between said connection portion and said joint portion at both said connected position and said disconnected position is provided on said joint portion.
A still another object of the present invention is to provide an ink jet recoding apparatus for recording by means of discharging ink onto a record sheet from a recording head comprising a first ink tank provided in the recording apparatus for storing ink a joint portion connected to said first ink tank a second ink tank disposed to be movable against said first ink tank, being provided with a connection portion connected to said joint portion in order to make ink supply from said first ink tank possible and a carriage for reciprocating with the recording head and said second ink tank mounted thereon, wherein said joint portion is movable between a connected position where said connection portion is connected thereto and a disconnected position where said connection portion is not connected thereto, and a cap member for sealing a region between said connection portion and said joint portion at both said connected position and said disconnected position is provided on said joint portion.